This invention relates to a disc cartridge, and more particularly to a disc cartridge having a disc-like medium such as an optical disc, a magneto-optical disc or the like rotatably received in a casing and including a shutter arranged so as to selectively close openings of the casing which permits a recording/reproducing device of a recording/reproducing apparatus to be accessible to the disc-like medium.
In general, a disc cartridge having a disc-like medium such as, for example, a magnetic disc, an optical disc, a magneto-optical disc or the like received therein is kept charged in a recording/reproducing apparatus in use. Unfortunately, such a disc cartridge conventionally tends to readily cause adhering of dust or the like thereto and damage thereto during handling thereof. Also, it is substantially affected by a variation in temperature. Thus, the disc cartridge typically includes a shutter slidably arranged so as to hold openings of the casing such as a head insertion hole, a drive shaft insertion hole and the like open in use and hold them closed in non-use.
In the conventional disc cartridge including such a shutter as described above, the shutter is adapted to be slid on an outer surface of the casing. For this purpose, the shutter includes an upper plate arranged so as to be opposite to an outer surface of an upper casing member and a lower plate opposite to that of a lower casing member, as well as a connection plate for connecting the upper and lower plates to each other therethrough, resulting in being formed to have a substantially U-shape in section. The lower plate is provided thereon with two holding pawls in a manner to be spaced from each other at a predetermined interval in a direction of sliding of the shutter. The holding pawls are engagedly fitted in a recessed slide groove of the lower casing member to guide sliding of the shutter on the casing and prevent dislocation of the shutter therefrom. Also, the upper and lower casing members are so formed that side surfaces thereof opposite to an inner surface of the connection plate of the shutter are flush with each other and the upper and lower plates are bent at substantially the same angle from the connection plate.
Nevertheless, the side surface of the upper casing member is often caused to be outwardly projected as compared with the side surface of the lower casing member due to a variation in dimensions of molding dies for the casing and shutter, a variation in molding conditions thereof, a slight amount of misregistration between the upper casing member and the lower casing member during assembling of the disc cartridge, and the like. Also, the conventional disc cartridge causes an angle of bending of the upper plate from the connection plate to be increased as compared with that of the lower plate therefrom. This causes each of the holding pawls provided on the lower plate of the shutter to be caught on an inner surface of the slide groove and the connection plate to be caught on the side surface of the upper casing member, leading to a failure in smooth sliding of the shutter on the casing. Also, it hinders smooth mounting of the shutter on the casing, resulting in assembling of the disc cartridge being deteriorated.